/Engine/Source/Editor/UnrealEd/Classes/ThumbnailRendering/SkeletalMeshThumbnailRenderer.h
The current default of Realtime maintains legacy behavior, but is overally agressive / for frequent than needed for most.
ThumbnailRenderer-specific frequency for thumbnail updates
virtual EThumbnailRenderFrequency GetThumbnailRenderFrequency ( [UObject](API\Runtime\CoreUObject\UObject\UObject) * Object ) const